Power Problems Defined and Explained

Power Problems Defined and Explained

Power problems within a mains power supply can result from environmental factors, local site and load conditions. Poor power quality can result in data processing errors, system malfunctions, wear and tear and eventual breakdown. The key factor when selecting a power solution is to identify the type of power problems a site is experiencing and their frequency and magnitude. Mains power failures are the most evident form of power quality issues, whether momentary or of a long duration. However there are other power problems which can pollute a mains power supply when it is present including


are short duration reductions in the mains power supply voltage below the nominal UK and European operating levels (230Vac single-phase or 400Vac three-phase in the UK), that can last for several cycles. For switch-mode power supplies, sag voltages can result in more current being drawn form the mains power supply to deliver the required output, resulting in component stress and heat. Possible causes of sag voltages include: heavy-inductive load switching such as air-conditioners and industrial motors


are longer duration periods of a sag voltage and can last for several hours and even days. Brownouts are common in areas with long overhead line runs.

Spikes and Transient Voltages

are fast-moving, high energy bursts (sometimes in excess of 6kV) that can damage switch-mode power supplies, connected loads and disrupt operations. Potential causes include local lightning strikes, electrical storms, load shedding, thermostatic switching, fluorescent lights and inductive motors.

Blackouts, Outages and Mains Power Supply Failures

are a total loss of mains electrical power that can last from several seconds, hours, days or even longer. Short-duration outages lasting longer than 10-30 seconds can cause a switch mode power supply to fail or operate erratically leading to data processing errors and loss of system integrity.

Potential Power Solutions

There are several power solutions available and the summary table below gives some indication as to the types of problem each of the three main groups can solve. Within each product group is a range of topologies and approaches, offering solutions to meet various specifications and budgets. Please refer to our Power Solutions Guide for further explanation or individual power protection product specifications.


are short duration, sudden increases in the mains power supply voltage level which can last for several cycles. Surge voltages can result in the automatic surge protection devices built-into sensitive loads, tripping to their systems. This can lead to a sudden system crash. The long term exposure of a load switch mode power supply to surges will result in wear and tear and component failure. Again heavy-inductive loads switching on/off can cause surge voltages.

Frequency Variations

are variations in the nominal supply frequency and are commonly associated with older, ill-maintained generators or the first few cycles of a generator on start-up.

Each of these power problems is included within our Power Terms Glossary along with a host of other definitions and expanded abbreviations. EcoPowerSupplies.com also provide both hardware and service solutions for power quality analysis and data logging.

Electrical Noise

is classed into one of two types (a) Common Mode which is a disturbance between the mains power supply lines and earth (phase-to-earth or neutral-to-earth) or (b) Normal Mode which is a disturbance between phase and neutral. Electrical noise can lead to switch mode power supply failure and disruption of their operation. Potential causes can include flickering lights, switchgear and cable faults and malfunctioning electronic systems.


are waveforms (voltage or current) superimposed onto the fundamental mains power supply waveform. In the UK and Europe the fundamental frequency is 50Hz (50 cycles per second) and harmonics are ordered into the following sequence – 2nd Harmonic 100Hz, 3rd harmonic 150Hz etc. Harmonic pollution can result in a distorted mains power supply voltage, overheating in building switchgear and electrical circuits, and circuit breaker nuisance tripping. Harmonic pollution in the UK is governed by G5/4-1 published by The Energy Networks Association.

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